who the article Electronics - My friend the soldering iron has already read, perhaps has. noticed that you can actually write quite a lot about this topic. And it's all about connecting two contact surfaces correctly. Separating these already connected contact surfaces is a completely different matter.
With simple components and connected lines, the connection is quickly broken. With multi-pin SMD components, on the other hand, it can be more difficult.
The following article should at least provide an introduction to many “separation situations”.
Safety instructions
I know the following notes are always kind of annoying and seem unnecessary. Unfortunately, many people who knew "better" have lost eyes, fingers or other things due to carelessness or injured themselves. Data loss is almost negligible in comparison, but even these can be really annoying. Therefore, please take five minutes to read the safety instructions. Because even the coolest project is not worth injury or other trouble.
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Requirements
Helpful articles:
You can find more helpful information on the basics of soldering in the following article:
Electronics - My friend the soldering iron
You can find more specific information about SMD and THT soldering in the following articles:
Electronics – Solder SMD components by hand
Electronics – Solder THT components by hand
Required material:
In the following list you will find all the parts you need to implement this article.
Required tool:
In the following list you will find all the tools you need to implement this article.
The desoldering pump
Here is the first tool available in the desoldering battle against connected solder joints. The desoldering pump is a vacuum pump with which you can suck liquid solder out of holes.
For this purpose, the desoldering pump is tensioned before use. This tension can then be released in the right place. A spring released in this way pulls back a piston very quickly, which sucks the liquid solder into the pump through the resulting vacuum.
Described like this sounds quite abstract, so here are a few instructions on how to use a desoldering pump.
Desoldering braid
The second useful tool in the fight against solder residue is the desoldering braid. Desoldering braid basically consists of a copper wire mesh soaked in flux. To desolder, the desoldering braid is placed on the solder to be removed and pressed against it with the hot soldering iron until the solder to be removed becomes liquid. The flux contained in the copper wire mesh then creates a capillary effect (a kind of suction effect) that sucks the liquid solder into the copper wire mesh of the desoldering braid.
Tongs
It may not be obvious at first glance, but pliers are also excellent helpers. They are ideal for removing incorrectly soldered pin headers. To do this, the solder at the soldering point of a pin header is made hot and the respective pin on the pin header is removed with pliers. But more on that later.
Removing THT components and pin headers
THT components (THT=Through Hole Technology=”through hole mounting”) are characterized by the fact that the contacts of the components are inserted through the board in the form of “legs” and soldered on the underside. This has two advantages: The components are very easy to solder and - once soldered - are connected to the circuit board in a very stable mechanical manner.
One of the disadvantages, however, is that desoldering is not always easy - especially for components with several components. It can happen that at least the component is damaged or destroyed. You will need a desoldering pump, possibly an electronic side cutter and needle-nose pliers.
First heat the first solder eye of the soldered component with the soldering iron.
Now try to suck off the liquid solder with the desoldering pump by placing the pump as vertically as possible over the soldering eye and “pressing”.
If you're lucky, the soldering eye will look like this. (EXAMPLE WITH CLEAN SOLDERING EYE)
However, it can also happen that the solder cannot be completely removed. This can happen, for example, with very small hole diameters or if the soldering eye in question is connected to a large copper surface. In the latter case, the solder cools down so quickly after removing the soldering iron that it cannot be completely vacuumed away.
Removal of SMD components
Removing simple SMD components with two contacts (such as resistors and capacitors) is often easy to do. Often even without damaging the respective component. With multi-pole SMD components such as RGB LEDs or ICs, however, things become more difficult.
Remove with soldering iron
Components with two contacts:
Heat the two contacts alternately for five seconds each with the soldering iron...
...until the solder slowly becomes liquid.
You then repeat this until...
...the component can be lifted off the circuit board.
Components with multiple contacts
“Bend one leg up” method:
With this method, the legs are individually heated and bent up from the printed circuit board so far that they are no longer connected to it.
“Cut off one leg at a time” method:
With this method, the legs are individually heated and snapped off to separate them from the circuit board.
“Solder bridge” method:
This method basically involves placing a large blob of solder over the contacts that need to be loosened. This means that all contacts can be heated at the same time and removed from the circuit board.
Remove with hot air
Desoldering with hot air is always advisable if the contacts of the component to be removed are either very difficult to reach with the soldering iron or if a large number of contacts have to be loosened. In both situations it is difficult to heat all legs at the same time. Desoldering with hot air is the solution to both problems. The component and the circuit board underneath are heated over a large area until the solder at all contact points has heated up to such an extent that the component can easily be lifted off the circuit board.
It is advisable to protect the surrounding components from the heat of the hot air. This works by taping or covering the surrounding components.
Place the circuit board with the component to be removed on a heat-resistant surface.
Now heat the component with hot air and check after a while whether...
...the component can be moved or lifted off.
Continue to heat the component and its contacts until it can be lifted off.
Cleaning soldering pads with desoldering braid
Once you have removed the unwanted components, you most likely have a very dirty printed circuit board in front of you. Flux residues can still be easily removed with a little isopropanol. More about this in the article Electronics - My friend the soldering iron.
However, when there are solder residues, the whole thing becomes much more complicated because they cannot simply be wiped off or scraped off. You should avoid the latter in particular because it can quickly tear off solder pads or even entire conductor tracks. To still get the solder off the circuit board, just a little bit of soldering wire is enough.
To do this, press the desoldering wire onto the dirty soldering pad with a soldering iron.
The underlying solder becomes liquid over time...
...and sucked into the desoldering wire by the resulting capillary effects.
Remove flux residue
Isopropanol is very suitable for removing flux residues. Flux residues always arise, especially with THT soldering. The flux sometimes “splashes” a little and actually always ends up on the surrounding circuit board.
A cotton swab is suitable for applying isopropanol even in small corners between the components.
Have fun with the project
I hope everything worked as described for you. If not or you have questions or suggestions please let me know in the comments. I will then add this to the article if necessary.
Ideas for new projects are always welcome. 🙂
PS Many of these projects - especially the hardware projects - cost a lot of time and money. Of course I do this because I enjoy it, but if you think it's cool that I share the information with you, I would be happy about a small donation to the coffee fund. 🙂
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